The present invention relates to a flow restricting structure in a displacement controlling mechanism of a variable displacement compressor that varies the inclination angle of a swash plate by adjusting the pressure in a control chamber, which accommodates the swash plate.
In a variable displacement compressor described in Japanese Laid-Open Patent Publication No. 8-338364, increasing the pressure in a control chamber, which is a crank chamber in the above publication, decreases the inclination angle of a swash plate, thereby reducing the displacement of the compressor. Decreasing the pressure in the crank chamber increases the inclination angle of the swash plate, thereby increasing the displacement of the compressor. The pressure in the crank chamber is controlled by supplying refrigerant from a discharge chamber to the crank chamber and releasing refrigerant from the crank chamber to a suction chamber. A control valve is located in a passage through which refrigerant is supplied from the discharge chamber to the crank chamber. The control valve controls the flow rate of refrigerant supplied from the discharge chamber to the crank chamber.
Refrigerant in the crank chamber continuously flows out through a passage for releasing refrigerant from the crank chamber to the suction chamber. The flow rate of refrigerant from the crank chamber to the suction chamber needs to be controlled by arranging a restrictor in the passage.
However, since the cross-sectional area of a restrictor needs to be small, it is significantly difficult to directly bore the restrictor in the passage. Alternatively, a restrictor may be formed in a metallic member that is fitted to the passage. In this case, the metallic member needs to be fitted in the passage accurately and tightly in contact with the passage. The metallic member therefore needs to be manufactured with high accuracy. This is troublesome and increases the manufacturing cost.
Accordingly, it is an objective of the present invention to provide an inexpensive and easy-to-form flow restricting structure in a displacement controlling mechanism of a variable displacement compressor.
To achieve the above objective, the present invention provides a variable displacement compressor for compressing refrigerant that is drawn into a suction pressure zone and discharging the refrigerant to a discharge pressure zone. The compressor includes a housing assembly, a drive shaft,a plurality of cylinder bores, a plurality of pistons, a swash plate, a supply passage, a pressure release passage, and a shutter. The housing assembly has a control pressure chamber. The drive shaft is rotatably supported by the housing assembly. The cylinder bores are formed in the housing assembly and are arranged about the drive shaft. Each piston is accommodated in one of the cylinder bores and defines a compression chamber inside the cylinder bore. The swash plate is tiltably accommodated in the control pressure chamber and reciprocates each piston inside the corresponding cylinder bore. Each piston compresses refrigerant that is drawn into the corresponding compression chamber from the suction pressure zone and discharges the refrigerant to the discharge pressure zone. The inclination angle of the swash plate is varied in accordance with the pressure in the control pressure chamber. The supply passage connects the control pressure chamber to the discharge pressure zone. Refrigerant in the discharge pressure zone flows to the control pressure chamber through the supply passage. The pressure release passage connects the control pressure chamber to the suction pressure zone. Refrigerant in the control pressure chamber is released to the suction pressure zone through the pressure release passage. The shutter closes one of the supply passage and the pressure release passage. The shutter is made of synthetic resin or rubber and includes a restricting passage.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.